Many types of exercise equipment and devices are currently in use to provide exercise for persons who want to stay physically fit and for persons with special physical or therapeutic needs. The stationary exercise bicycle is one of the best known of such exercise devices. Other types of equipment include various forms of treadmills, frame-like weight lifting stations, including pivotable or swingable components, and, more recently, exercise devices that simulate climbing stairs.
A person going up stairs does work, and burns calories, by raising the body's weight. Stair climbing exercise devices attempt to simulate the biomechanical activity and effect of climbing steps. In stair climbing devices, the exerciser's work typically is done by maintaining the body in the same place while the steps move, that is, by shifting body weight repeatedly from one foot to the other, optionally against variable resistance. The user's feet generally are received on moving or movable foot receiving members. Separate foot receiving members are common, either moving continuously in one direction or between an upper position and a lower position alternatively. In the latter, as one foot of the user presses down on a foot-receiving member in its upper position, that member is driven down against resistance. Generally, the second member will be rising at the same time. When the second member reaches its upper position, the user presses down on it with the other foot, raising the weight of the body, and driving the second member down.
Representative examples of fairly early stair climbing devices include those disclosed in U.S. Pat. Nos. 3,497,215 (to Harrison), 3,743,283 (to Garrett), 4,340,218 (to Wilkinson), 4,687,195 (to Potts), 4,555,108 (to Monterio), and 4,726,581 (to Chang). These patents reflect the development of stair simulators, disclosing substantially static steps (the Garrett and Wilkinson patents) or an escalator-like plurality of moving steps connected to endless chains (the Harrison, Chang and Potts patents). The patent to Monterio discloses two sets of circumferential steps mounted on a rotatable member.
Some stair devices, such as those disclosed in U.S. Pat. Nos. 3,970,302 (to McFee) and 4,496,147 (to DeCloux et al.), include a pair of reciprocally movable foot receiving supports carried by inclined track members. In use, the user steps on one foot support while removing weight from the second. The foot support without weight rises, while the support bearing weight descends at a rate determined by the resistance. When the downwardly traveling support reaches the end of travel, the user transfers his weight to the other foot and the motion of the supports reverses. The McFee and DeCloux et al. patents also disclose resistance systems, including shock absorbers or hydraulic systems, used in this type of device, and in stair simulators generally.
While the above prior art devices are useful, some of them are rather large for in-home use, they may not provide optimally comfortable aerobic exercise workouts, they require reciprocal leg motion, and they may be quite noisy.
U.S. Pat. No. 4,708,338 (to Potts) is directed to solving at least some of these problems by providing a stair climbing exercise apparatus, including a frame with a base and a plate attached to the base. A right and left pedal, on opposite sides of the plate, alternatively and independently oscillate between an upper rest position and a lower position attained by the weight of or force generated by the user. Each pedal is returned to its upper position by a spring. As the pedals travel downwardly, they drive a drive sprocket in one direction through right and left sprockets, including free-wheeling, one way clutches. Each sprocket is driven by a chain connected to the associated pedal at one end and to the return coil spring at the other end. A single continuous chain drivingly connects the drive sprocket and a transmission, in turn joined to an alternator that acts as a dynamic brake for providing resistance.
Somewhat similarly, the device disclosed in U.S. Pat. No. 4,938,474 (to Sweeney et al.) includes two pedals and two spring-biased chain and sprocket arrangements, one such arrangement associated with each pedal. The sprockets are mounted on one-way roller clutches so that as each pedal moves downwardly, the drive shaft is rotated only in one direction. A drive sprocket is secured to the drive shaft and drives a single endless chain, in turn connected to another sprocket mounted on a shaft on which a flywheel is mounted. The primary aspect of the Sweeney et al. apparatus is an automatic speed control system including a micro-controller.
U.S. Pat. No. 4,949,993 (to Stark et al.) is directed to solving problems associated with the roller chain and sprocket arrangements used in stair devices like those disclosed in U.S. Pat. Nos. 4,708,338 and 4,938,474 (to Potts and Sweeney et al., respectively). More specifically, the problem addressed by the Stark et al. patent is that the chains commonly used to connect the pedals to the one-way drive shaft tend to break. The Stark et al. solution is to provide a cable or "wire rope" and pulley wheel as the first portion of the force transmitting system. Two cables and one pulley are operably connected to each pedal, the first cable with one end secured to the pedal arm and the second end secured to the pulley, and the second cable with one end secured to the same pulley and the other end secured to a lengthy tension spring. As one cable moves the pulley by unwinding, the other winds into a groove on the pulley.
The Stark et al. device requires a large diameter sprocket wheel to maintain the speed relationship between the pedal motion and the flywheel motion. This is because the pulley wheels that receive the cables must have a larger working diameter to enable the required cable wrapping without undue lateral stresses being created in the cable. A problem only partially solved by the Stark et al. teachings is that in sprocket and roller chain arrangements, each sprocket tooth to chain engagement creates a feel of roughness. While the Stark et al. patent teaches that the chains connected to the pedal arms may be replaced by cables, a sprocket wheel and roller chain arrangement is still required. Additionally, a high spring force is required to maintain the pedal in contact with the user's foot, to prevent slack in the cables, and to compensate for cable stretch.
U.S. Pat. No. 5,033,733 (to Findlay) discloses another stair climbing exercise apparatus. The apparatus includes the typical arrangement of two side-by-side steps mounted on bars pivotally connected to a frame. A cable or strap connects each step to a spring-driven pulley. The pulleys are connected via a bushing and a one-way clutch to a drive shaft. The clutch is engaged only upon downward motion of the associated step to drive the shaft in one direction. The shaft in turn drives a multiple planetary gear arrangement, the output of which drives a rotary member having an electro-magnetic resistance element. With all the adjacent movable mechanical parts associated with the multiple planetary gear arrangement, the Findlay apparatus does not reduce lash to a minimum.
While the above-cited prior art generally reflects progressive improvement in stair climbing simulators, and the latter two patents (to Findlay and Stark et al.) solve some of the problems associated with prior art exercising devices, it is clear that with current stair devices smoothness, fluidity, safety and quietness are not optimized. There is a need for a reasonably priced, biomechanically and ergonomically sound stair climbing simulator or "stepper" exercise machine that the exerciser enjoys using because the machine is attractive, quiet, self-prompting and has a smooth, fluid motion.